Toneri or Oro is the most likely.
Among his parents was a well known figure or something like that I heard.
He could be some Shin/Oro like clone maybe.
He uses the soft body physique like Oro and his clothing, attitude and fighting feels a bit similar to Oro.
He could also be Toneri's son.
Toneri was welcome on earth at the end of the movie. Naruto and Hinata invited him to come.
He wanted to stay on the moon but maybe considered to have offspring and that the earth would be a better place for that offspring to live and grow compared to the moon, where only Toneri himself is the only one left (not a great place to grow up there, because of that). It would also make sure the Otsutsukis from the moon, can continue to expand on earth and not die out on the moon.
Kakashi, Kabuto and Jiraiya are not likely to be the father.
Mitsuki is said to be from a different village.
